Prof.
John
G. Rarity

Quantum
Photonics

Abstract

The
discoveries of Newton revolutionised our understanding of light and
his ideas were refined by others (including Young, Huygens, and
Maxwell) to form the wave description of light. This description was
rocked by the developments of quantum mechanics in the early part of
the 20th century and in particular by Einstein’s
discovery of the photon. This led on to concepts such as
wave-particle duality and entanglement. These counter-intuitive
properties even worried the likes of Einstein. Advances in technology
now make it routine for us to isolate and detect individual photons,
to test their quantum properties and illustrate Einstein’s
paradoxes in the laboratory. Key experiments have shown that light
can behave like a particle (photon) and a wave within the same
experiment. Similarly, photon pair experiments show that the pairs
have strongly correlated properties such that any measurement made on
one instantaneously sets a value for the other even when they are
separated by large distances (this is entanglement).

There
comes a point when we have to accept that QM is a good description of
nature at the microscopic level despite some bizarre properties. This
then begs the question, how can we use these properties to our
advantage. This search has led to ways of sending information encoded
on single photons, to quantum teleportation schemes and eventually to
the quantum computer. We are now trying to build
the fundamental gates of such a machine based on single photons
encoding bits of information. In this talk I will introduce the
concept of the photon and its use to carry information. I will go on
to discuss how it can be used for communication and computing and
some technologies for creating single photons and photon pairs
suitable for use in these schemes.